The end of Chapter 12 is a HUGE leap in character growth for Hinako! Sure, she's not outright confessing her feelings to Asahi, but she is at least asserting herself, taking advantage of the opportunity Asahi has provided for her, and stating her desires (in a sense, at least, by saying "I want to have you all to myself").
This manga is another great stride in representation in yuri manga! Hinako realizes that she is in love with Asahi, though she doesn't necessarily feel sexual attraction, at least not yet. This suggests that Hinako MIGHT be asexual/homoromantic, or she could be a demi-sexual lesbian. It was very clear from the early part of the manga that she has NEVER felt either sexual or romantic attraction to men. Over the course of the 12 chapters so far, it is clear that she DOES feel a romantic attraction toward Asahi. However, she seems to be wavering about whether she is interested in a physical relationship. Of course, we really don't know what Asahi's position is on any of this since she has pretty much closed herself off from relationships of any sort in order to be mother, father, and older sister to Subaru.
I really am looking forward to the next chapter! I expect it will reveal some hidden emotions at least!